Optically driven spin-alignment precession

TL;DR

This paper investigates a less common form of optically driven spin precession using linearly polarized light, revealing its characteristics in cesium vapor and the impact of buffer gases on the signal.

Contribution

It introduces and experimentally characterizes a novel type of optically driven spin precession not involving coherent magnetization precession.

Findings

Spin-alignment precession signal is comparable to classical spin-orientation in vacuum cells.

Buffer gases significantly suppress the spin-alignment precession signal.

Spin mixing of excited states explains the observed effects.

Abstract

The effect of optically driven spin precession discovered by Bell and Bloom [W. E. Bell and A. L. Bloom, Phys. Rev. Lett. 6, 280 (1961)] is widely used nowadays as a basis for numerous experiments in fundamental physics and for diverse applications. In this paper we consider a much less popular version of the light-induced spin precession that does not imply coherent precession of the spin-system magnetization and is excited by linearly (rather than circularly) polarized light. Pump-probe measurements performed on the D2 line of cesium vapor show that the magnitude of the signal of the optically driven spin-alignment precession, in "vacuum" cells (with no buffer gas) is close to that of classical spin-orientation precession. In the presence of buffer gas, however, the signal of spin-alignment precession appears to be strongly suppressed. The discovered effect is ascribed to spin mixing of excited states of cesium atoms in the cycle of optical pumping.